Buffer strips perform well in new study

A new take on a fairly common conservation practice can do a lot more than previously thought to control nutrient runoff in crop fields, according to new research in Iowa.

A project testing the viability of riparian buffer strips to remove nutrients from crop runoff water was conducted this growing season by the Ames, Iowa-based Leopold Center for Sustainable Agriculture. The main target for the research was a 1,000-foot stretch of Bear Creek in Story County, Iowa, where a "saturated buffer" was installed to catch tile-line water before it's released into waterways.

The system uses "a shallow lateral line" that "has control structures that raise the water table and slow outflow, allowing the buffers to naturally remove nutrients such as nitrate and phosphorous."

The results: In addition to curbing over half of the immediate tile line outflow into waterways, it removes all of the nitrate output, says USDA National Laboratory for Agriculture and the Environment and lead researcher for the project Dale Jaynes.

"The system removed 100% of the nitrate from 60% of the field tile flow,” Jaynes says. "We figure that 250 kilograms, or about 500 pounds, of nitrate nitrogen was kept out of the stream."

The future of this type of runoff water control, which Jaynes says he originally expected to divert just 10% to 15% of field tile runoff water, has a lot of promise in the right situations.

"You would need a lot of these at different points along a stream to make a difference in water quality, but this is a start," Jaynes says. "This is a technology that many people definitely are interested in, and in having more information about how they work."